Click App Catalog and select Apps for SharePoint. (If we are installing apps for the first time in SharePoint, we need to create a new app catalog first to contain the apps.)

Click Upload.

The file we will upload can be downloaded from here or by copy-pasting this link on a browser tab: https://files-manywho-com.s3.amazonaws.com/bb03e922-8a39-46e8-b492-aacd2ccb5a42/BoomiFlowsApp.app) Click Chose Files and upload this file.